PT Unknown
AU Bahrenburg, J
TI Ultrafast Photochemical Dynamics of Azobenzenes Affected by Intra- and Intermolecular Interactions and of a Proton Transfer Switch
PY 2014
PU Christian-Albrechts-Universität zu Kiel
WP https://macau.uni-kiel.de/receive/diss_mods_00015190
LA en
DE Femtosecond Spectroscopy; Photochemistry; Molecular Switches; Molecular Dynamics; Femtosekundenspektroskopie; Photochemie; Molekulare Schalter; Molekulare Dynamik
AB The main goal of this Thesis was the investigation of the photochemical properties and ultrafast isomerization dynamics of several azobenzene (AB) derivatives under the influence of different intra- and intermolecular effects by means of femtosecond time-resolved absorption and fluorescence spectroscopy. The influence of electron donating and accepting substituents on the electronic relaxation was investigated for a push-pull AB. The dynamics of the push-pull AB and a bifunctional AB were also investigated with the chromophores covalently attached to tightly cross-linked polymer colloids. Due to the strong intermolecular mechanical forces acting on the photoexcited ABs, the excited state lifetimes in the polymeric were found to be dramatically longer compared to the lifetimes in solution. A systematic study on possible intramolecular interactions between chromophores was performed for two multi-azobenzene compounds. Transient absorption anisotropy decay measurements allowed to obtain insight into intramolecular chromophore-chromophore interactions on the time scale of several tens of femtoseconds. The data provide clear evidence for strong electronic coupling. The ultrafast dynamics of a magnetically bistable nickel porphyrin functionalized with an azopyridine as photoswitchable unit were investigated to obtain insight into the isomerization mechnanism and a possible switch of the spin state of the nickel ion. Furthermore a bistable excited state intramolecular proton transfer (ESIPT) switch was investigated. The data clearly suggest a stepwise formation of the desired proton transfer product via two intermediate states.
PI Kiel
ER